Chemical vapor deposition and etching techniques are utilized in a wide variety of applications. For example, these techniques are used in the manufacture of electrical components. Specifically, chemical vapor deposition and dry etching techniques are used in the manufacture of semiconductor devices and integrated circuits to deposit or etch layers of silicon dioxide and other like material on semiconductor substrates. Chemical vapor deposition is also utilized to impart a reflective or anti-reflective coating to optical devices. In mechanical applications, chemical vapor deposition is employed to impart wear resistant coatings or to impart coatings that increase hardness or reduce friction. In chemical applications, vapor deposition is used to produce barriers to diffusion or as a protection against oxidation or corrosion.
As is well known in the art, chemical vapor deposition and etching techniques comprise a series of sequential steps. First, a source of vapor or vapor material is provided. The source of the vapor material is usually a vapor or a gas, although a solid or liquid material may be utilized if it is first vaporized. Next, the material is transported to a substrate wherein the transportation step may take place in a partial vacuum or a high vacuum. In the transportation step, an important consideration is uniformity of the arrival rate over the substrate. If this step of the process is not properly controlled, uneven or nonuniform film thickness across the substrate can result and produce defective parts. The next step is the reaction of the chemical vapor with the substrate resulting in the deposition of an etching film. The substrate is often heated to increase the reactivity of the substrate for the vapor thereby facilitating the process. The reactants flow over the heated substrate surface and react at the substrate surface to deposit a film or to etch the surface.
In single wafer systems (e.g. for deposition of Si substrate wafers), different effects and particularly gas depletion can lead to non-uniformities across the surface of the substrate, as earlier mentioned. These non-uniformities are frequently manifested by either a differing degree of film deposition or etching near the center of the substrate as compared to the edge. This effect gets more and more severe with increasing diameters of substrate. The effect is particularly pronounced when a Si wafer substrate that approaches or exceeds 300 mm in diameter is employed. Such non-uniformities of film deposition or etching can lead to various problems. For example, in the manufacture of semiconductors and integrated circuits, such non-uniformities can result in devices that do not function or function with less than optimal results.
The prior art has provided various solutions to the problem of nonuniform film deposition or etching at the surface of the substrate. One such solution is to utilize different gas distribution plates or focus rings to compensate for nonuniform film deposition or etching. A disadvantage to this approach is that finding the correct gas distribution plate or focus ring for a particular process can be very time consuming and thus costly. This approach is time consuming because it requires hardware in the reaction chamber to be exchanged. In addition, the appropriate gas distribution plate for a particular process may not be appropriate for another process. Consequently, in order to use the same system for a different process, the user must change the gas distribution plate which results in expensive down time.
It is therefore an objective of the present invention to provide an improved apparatus and method for chemical vapor deposition and dry etching that minimizes the non-uniformity of the deposited film across the surface of a substrate and does so without the use of focusing rings and without the necessity of changing the gas distribution plate.